From: Jiri Olsa <jolsa@redhat.com>
To: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>
Subject: [PATCH 2/8] x86/ftrace: Remove fault protection code in prepare_ftrace_return
Date: Tue, 31 Aug 2021 11:50:11 +0200 [thread overview]
Message-ID: <20210831095017.412311-3-jolsa@kernel.org> (raw)
In-Reply-To: <20210831095017.412311-1-jolsa@kernel.org>
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Removing the fault protection code when writing return_hooker
to stack. As Steven noted:
> That protection was there from the beginning due to being "paranoid",
> considering ftrace was bricking network cards. But that protection
> would not have even protected against that.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
arch/x86/kernel/ftrace.c | 38 +++-----------------------------------
1 file changed, 3 insertions(+), 35 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 1b3ce3b4a2a2..c555624da989 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -625,12 +625,10 @@ int ftrace_disable_ftrace_graph_caller(void)
* Hook the return address and push it in the stack of return addrs
* in current thread info.
*/
-void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
+void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
unsigned long frame_pointer)
{
unsigned long return_hooker = (unsigned long)&return_to_handler;
- unsigned long old;
- int faulted;
/*
* When resuming from suspend-to-ram, this function can be indirectly
@@ -650,37 +648,7 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
- /*
- * Protect against fault, even if it shouldn't
- * happen. This tool is too much intrusive to
- * ignore such a protection.
- */
- asm volatile(
- "1: " _ASM_MOV " (%[parent]), %[old]\n"
- "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
- " movl $0, %[faulted]\n"
- "3:\n"
-
- ".section .fixup, \"ax\"\n"
- "4: movl $1, %[faulted]\n"
- " jmp 3b\n"
- ".previous\n"
-
- _ASM_EXTABLE(1b, 4b)
- _ASM_EXTABLE(2b, 4b)
-
- : [old] "=&r" (old), [faulted] "=r" (faulted)
- : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
- : "memory"
- );
-
- if (unlikely(faulted)) {
- ftrace_graph_stop();
- WARN_ON(1);
- return;
- }
-
- if (function_graph_enter(old, self_addr, frame_pointer, parent))
- *parent = old;
+ if (!function_graph_enter(*parent, ip, frame_pointer, parent))
+ *parent = return_hooker;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
--
2.31.1
next prev parent reply other threads:[~2021-08-31 9:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-31 9:50 [PATCH 0/8] x86/ftrace: Add direct batch interface Jiri Olsa
2021-08-31 9:50 ` [PATCH 1/8] x86/ftrace: Remove extra orig rax move Jiri Olsa
2021-08-31 9:50 ` Jiri Olsa [this message]
2021-08-31 9:50 ` [PATCH 3/8] x86/ftrace: Make function graph use ftrace directly Jiri Olsa
2021-08-31 9:50 ` [PATCH 4/8] tracing: Add trampoline/graph selftest Jiri Olsa
2021-08-31 9:50 ` [PATCH 5/8] ftrace: Add ftrace_add_rec_direct function Jiri Olsa
2021-08-31 9:50 ` [PATCH 6/8] ftrace: Add multi direct register/unregister interface Jiri Olsa
2021-09-14 21:35 ` Steven Rostedt
2021-09-16 19:45 ` Jiri Olsa
2021-08-31 9:50 ` [PATCH 7/8] ftrace: Add multi direct modify interface Jiri Olsa
2021-09-14 21:41 ` Steven Rostedt
2021-09-15 21:47 ` Steven Rostedt
2021-09-16 19:49 ` Jiri Olsa
2021-09-16 20:41 ` Steven Rostedt
2021-08-31 9:50 ` [PATCH 8/8] ftrace/samples: Add multi direct interface test module Jiri Olsa
2021-09-01 15:23 ` [PATCH 0/8] x86/ftrace: Add direct batch interface Alexei Starovoitov
2021-09-01 19:06 ` Jiri Olsa
2021-09-02 14:54 ` Steven Rostedt
2021-10-08 9:13 [PATCHv2 " Jiri Olsa
2021-10-08 9:13 ` [PATCH 2/8] x86/ftrace: Remove fault protection code in prepare_ftrace_return Jiri Olsa
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